RE: (ET) walk behind electric tractor?

["Elie, Larry (L.D.)" <lelie ford com>]

Before you get too excited, it's 1/2 hp folks.  Rule of thumb; an electric 
motor can replace a gas engine of twice it's hp (assuming the electric hp 
is 'honest'...) so it should be equivalent to a 1 hp tiller... hmm... too 
wimpy for much work.  The smallest Troy-Built Pony is 3.5 hp I think.  The 
reason of course is that the cells are pretty small to charge anything.  
BTW, many electric hp ratings are trash; Sears is probably the worst.  I 
have used a '4.5 hp peak' saw that was 12 Amps at 110v.  Now 12A * 110v = 
1320 watts.  760 watts is 1 hp IF everything is perfect; it isn't.  
Typically it takes 1000 electrical watts to produce 1 hp for small AC 
motors.  They claim the peak wrong; they use peak voltage * peak current 
(you are only entitled to use RMS values unless you can manage square-wave 
current) and STILL don't get those numbers.  They take that value, add in 
the inertia of the motor to stall ('brake' hp, sort of) and factor in 
that, then they round up.  That 4.5 hp pe!
ak sears saw is probably 1 to 1.2 hp.  Now I expect this tiller is really 
an HONEST 1/2 hp, but it is still a bit wimpy to do serious work.  The GE 
big tiller runs 70 A at 36 V continuously, and the breaker trips at 100 A 
at 36 V after a few minutes (you can go way over 100 A for over a minute 
though) so I get around 3500 watts; still only about 4 to 5 hp, which 
compares very well to an old Sears tiller I had behind a tractor of the 
SAME width that used an 8 hp gas engine; the old 2-1 rule.  I don't know 
the rating of the little GE tiller.

Larry Elie


-----Original Message-----
From: Jim Coate [mailto:jbc coate org]
Sent: Thursday, February 13, 2003 10:11 PM
To: elec-trak cosmos phy tufts edu
Subject: (ET) walk behind electric tractor?



While searching for electric tractor information on the web, I stumbled 
upon the "Sun Horse" walk-behind electric tractor. There are a variety 
of tools to plow, seed, cultivate, and haul, and the variable-speed 
drive reportedly allows for precise "surgical weeding".

Has anyone seen such? This is a new one to me.

See http://www.freepowersys.com/shorse.htm


_________
Jim Coate
1992 Chevy S10
1970's Elec-Trak
http://www.eeevee.com